Good move.
This might spark some debate, but IMHO it's just a matter of time before they either phase out the 2500 series or come up with something more heavy-duty than the 3500 and renumber everything. Kind of like how they appear to be phasing out the regular cab in some configurations.
This 3500 rides smoother than the previous year 2500, and the cost isn't that much more. Haven't driven an 03 2500, but I can't imagine the ride being much, if any, softer than the 3500.